In a typical electrical distribution system, an electrical energy supplier or utility company generates electrical energy and distributes the electrical energy to consumers via a power distribution network. The power distribution network is the network of electrical distribution wires which link the electrical supplier to its consumers. At the consumer""s facility, there will typically be an electrical energy meter, such as a revenue meter, connected between the consumer and the power distribution network to measure the consumer""s electrical demand. The revenue meter is an electrical energy measurement device which accurately measures the amount of electrical energy flowing to the consumer from the supplier. The amount of electrical energy measured by the meter is then used to determine the compensation due to the energy supplier.
Even for meters which provide remote communications capabilities, it is often necessary to interact directly with the meter locally, such as to program or configure the meter and/or to upload and/or download data stored in the meter. One method of providing a local user interface to the revenue meter involves utilizing optical communications. Optical Ports, using both the visible and/or infra-red portions of the spectrum, are used on energy meters to allow a quick data and command connection point for a user who is physically proximate to the meter. Further, as will be discussed below, such an optical connection allows a user to electronically interface with the meter without comprising the meter""s environmental or security protection provisions.
Typically, the optical port is located on the front of the meter such that the user can connect an optical probe/coupling, such as the U.S. Microtel PM-250, manufactured by U.S. Microtel located in Richardson, Tex., between the meter and their personal computer or other data gathering device. One exemplary probe contains infrared emitting and receiving diodes that xe2x80x9coptically matexe2x80x9d with opposing infrared emitting and receiving diodes located in the optical port of the meter to transmit to and receive data. Energy meters typically have infrared emitting and receiving diodes mounted on the meter""s front most printed circuit board where they are both physically and visibly accessible.
In the past, optical ports have been implemented in a variety of ways. Typically, a meter features an injection molded cover for the meter that is made with clear or colored plastic-type material. The optical port is fabricated separately from the meter cover and subsequently fastened to the cover through a secondary operation such as with screws, or press fit, or ultrasonically inserted into the cover, etc. Such secondary operations are costly and require tight tolerances to maintain quality and function. Germer et al, U.S. Pat. No. 4,491,793, discloses an exemplary two piece detachable magnetic coupler which incorporates optical communications.
Further, an advantage of optical based communications is the ability to place the meter""s infrared diodes behind the meter cover to environmentally protect them, as well as the other meter electronics, while still making them visibly accessible. As will be appreciated, however, enclosing the infrared diodes may impede the transmission of the optical signals between the transmitter and receiver. Typical optical port designs, known in the art, have taken measures to improve the light transmission through the meter cover between the diodes and the optical device coupled with the port. However, problems still exist when manufacturing or assembling the meter cover and attaching the meter cover to the main body of the meter containing the meter electronics and optical transceivers since tolerances in both the manufactured parts and the assembly process may cause the internal structure of the assembled meter, and therefore the optical transceivers, to misalign with the cover and the portion thereof defining the optical port, for example, lean or twist with relation to the cover. This may result in misalignment between the optical probe and optical transceivers when the probe is coupled with the meter.
U.S. Pat. No. 5,861,742 (Miller) describes an integrally molded optical port having light pipes disposed in the cover, the light pipes being aligned with the emitting and receiving diodes of the device electronics and an optical probe coupled with the optical port. Light pipes are designed to transmit light from a source, through a transparent pipe, and to an outlet using total internal reflection in the pipe interface to keep the light beams within the light pipe. One disadvantage of this approach is that the alignment of the light pipes to the meter""s infrared diodes is critical and tolerances must be kept very tight. A slight offset in alignment can mean failure of light transmission and allow external light to interfere with the operation of the optical port. Further, the use of light pipes requires that the side walls of the light pipes be extremely defect free or the optical transmission may degrade by loss due to scattering. To combat this, some designs utilize a dark material to block interfering light from the light being transferred between the Optical Port and the Optical Probe, however this adds to the assembly and part cost. Other designs utilize cylindrical tubes to direct the light to and from the meter and the optical probe.
Still other designs take the infrared diodes from the meter and place them directly into the fastened optical port. However, all present designs have to deal with the functional limitations of infrared diodes. For example, the diode""s light signal strength is limited and, therefore, the path from an emitting diode to a receiving diode must be very clear of obstructions and must be aligned with the light transmission means.
Thus, there is the need for an improved meter cover that provides an optical port having a lower manufacturing cost and improved tolerances for transceiver signal strength and alignment, while maintaining the cover""s environmental and tamper resistant integrity.
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiments described below relate to an electric meter cover comprising an optical port, the optical port operative to allow transmission of an optical signal through the electric meter cover, the optical port further comprising a lens operative to focus the optical signal.
The preferred embodiments further relate to a method of transmitting signals between an electric meter housed within a cover and external an optical device, the cover having at least one lens, the electric meter including a diode located proximate to the lens. In one embodiment, the method comprises coupling the optical device to the cover, transmitting the signal from said diode through the lens, whereby the lens is operative to focus the signal proximate to a receiving diode located external to the cover.
Further aspects and advantages of the invention are discussed below in conjunction with the preferred embodiments.